enableSharding¶

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Definition
Syntax
Behavior
Example

Definition¶

enableSharding¶

Note

Changed in version 6.0.

Starting in MongoDB 6.0, this command is not required to shard a collection.

The enableSharding command explicitly creates a database.

The mongosh method sh.enableSharding() wraps the enableSharding command.

Syntax¶

The enableSharding command has the following syntax:

Recommended. Specify the database to create:

copy

db.adminCommand( {
   enableSharding: "<database name>"
} )

Optionally, starting in MongoDB 4.2.2 (and 4.0.14), you can include the primary shard specification in the command, although this is not recommended:

copy

db.adminCommand( {
   enableSharding: "<database name>",
   primaryShard: "<shard name>"  // Available starting in MongoDB 4.2.2 (and 4.0.14)
} )

You can only run the enableSharding command on the admin database from a mongos instance.

Fields¶

The command takes the following fields:

Field

Type

Description

enableSharding

String

The database you want to use. The database is created if it does not exist.

primaryShard

String

Optional. The primary shard for the database; the primary shard contains the unsharded collection for this database. In general, rather than explicitly specifying the primary shard, it is recommended to let the balancer select the primary shard instead.

Warning

Tip

In general, you should not need to specify the primary shard. Allow the balancer to select the primary shard instead.

Available starting in MongoDB 4.2.2 (and 4.0.14)

Returns¶

The command returns a document that contains status of the operation.

Behavior¶

Write Concern¶

mongos uses "majority" for the enableSharding command and its helper sh.enableSharding().

Primary Shard¶

In general, you should not need to specify the primaryShard in the command. Instead, allow the balancer to select the primary shard.

However, if you do specify the primaryShard in the command for a database and the database is already sharding enabled with a different primary shard, the operation returns an error and the primary shard for the database remains as before. To change the primary shard for a database, use movePrimary instead.

Example¶

The following command, run from a mongos, creates the the shardTest database:

copy

db.adminCommand( { enableSharding: "shardTest" } )